1. Field of the Invention
The present invention relates to a storage control subsystem that comprises one or more storage devices or a logical volume access management method for a storage control subsystem. The present invention also relates to a storage system that comprises a storage control subsystem and a host that is connected to the storage control subsystem.
2. Description of the Related Art
For example, in a business-critical storage system that handles a large volume of data, data is managed by using a storage control subsystem that is formed separately from the host computer (hereinafter referred to simply as the ‘host’) This storage control subsystem is also known as a disk array device, for example, and is a RAID (Redundant Array of Independent Inexpensive Disks) system that is constituted by arranging a multiplicity of disk-type storage devices in the form of an array.
As an example of a storage system, a technology is known (Japanese Patent Application Laid-Open No. 2001-195201) for collectively changing, with respect to a plurality of volume pairs that are established extending over disk devices controlled by a plurality of disk control devices, the states of all the volume pairs by means of a single state change request from an upper layer host or operating panel or an event-driven state change request that is generated within a single disk control device, irrespective of the number of installed disk control devices, disk devices, and so forth.
Further, in a storage control subsystem, for example, data is copied from a first logical volume to a second logical volume that forms a pair (hereinafter the first logical volume that constitutes the copy source will be called the ‘regular volume’, while the second logical volume constituting the copy destination will be called the ‘subvolume’). In this case, in order to perform copying to the subvolume normally, the subvolume must enter an offline state in which same is not connected to any host. This is because, when data is copied to a subvolume that is in an online state, other data is written from the host to the subvolume during the copying process and hence there is the risk that the data in the subvolume will not be the same as the data in the regular volume.
A method of preventing this risk that may be considered is one in which data is not copied to the subvolume when the subvolume is in an online state.
However, accordingly, when a plurality of regular volumes constitute a single copy source, a plurality of subvolumes constitute a single copy destination, and copying is performed with respect to this plurality of subvolumes, for example, even if just one of the plurality of subvolumes is in an online state, although copying may be performed normally to the other subvolumes in an offline state, copying to subvolumes in an online state is not executed, and therefore data integrity cannot be preserved between the plurality of regular volumes (the copy source) and the plurality of subvolumes (the copy destination).
In order to prevent this situation from arising, before data in a regular volume constituting the target is copied, a subvolume that is paired with this regular volume must enter an offline state. In this case, if the subvolume is connected to at least one host, the user must find the connection-destination hosts of the subvolume individually. In order to find the connection destination hosts, for example, a first user of a first host that outputs a copy command must consult, by telephone or otherwise, second users of a plurality of second hosts that are possibly connected to the subvolume, with regard to which logical volume these second hosts are connected to. Then, once the connection-destination second hosts are known, the second user must render the subvolume offline by breaking the connection of the second hosts with the subvolume.
Likewise, when the subvolume is in the online state, normal copying cannot be executed, and processing that is troublesome for the user is required in order to change the online state of the subvolume to the offline state. This process becomes increasingly difficult as the number of subvolume connection-destination hosts increases.